Cabot appeared in nearly one hundred feature films. He made his debut in 1931 in an uncreditedbit part in an episode of the serialHeroes of the Flames. In Ann Vickers (1933), he portrays a soldier who seduces a naive woman (Irene Dunne) and gets her pregnant as he leaves for the war. He then appeared in King Kong (1933), which became an enormous success and established Cabot as a star.

He tested for the lead role of The Ringo Kid in John Ford's Stagecoach (1939), but John Wayne got the part.[4] A consistent box office draw, Cabot appeared in many movies at many studios before leaving Hollywood to serve in World War II.

Cabot was married three times, in Florida to Mary Mather Smith with whom he divorced prior to moving to Hollywood, and to actresses Adrienne Ames and Francesca De Scaffa.[citation needed]

He was one of Errol Flynn's social pack for several years but they fell out during the production of the unfinished The Story of William Tell. Flynn was producing the film and asked Cabot, whom he described as "an old, old pal," to perform in it, knowing that Cabot was finding it hard to get work in Hollywood at that time. However, when Flynn's production partners defaulted, the production halted, leaving Flynn stranded in Rome facing financial ruin. Cabot, in an attempt to get paid when other cast members were working without pay, had Flynn's and his wife Patrice Wymore's personal cars and clothing in their Rome hotel seized. Flynn wrote angrily in his autobiography of what he termed Cabot's "betrayal."[5]Eleven years after Flynn's death, in an interview in England in 1970, Cabot paid tribute to him as a critically underestimated actor, but said that Flynn had destroyed himself through narcotic addiction.[citation needed]